1. Field of the Invention
The present invention is generally concerned with clutch release bearings, in particular those for automobile vehicles.
It is more particularly directed to so-called "pull" type clutch release bearings which are designed to operate in traction on the clutch release device of the clutch to be operated and which are coupled to this device for this purpose.
2. Description of the prior art
In some clutch release bearing assemblies, and in particular in the clutch release bearing assembly described in French Pat. No. 2 304 826 and that described in U.S. Pat. No. 4,648,499 commonly assigned with this invention it has been proposed to use between the clutch release bearing and the clutch release device to be operated, in order to couple the clutch release bearing to the clutch release device, a part referred to hereinafter for convenience only as the "coupling part" or "action part" which, appropriately attached to the clutch release device, comprises on the side of the latter opposite the clutch release bearing a radial bearing flange through which it is adapted to operate on it, in cooperation with fastening means operative in traction between a coupling part of this kind and a part referred to hereinafter for convenience only as the "drive part" forming part of the clutch release bearing, adapted to provide an axial coupling between said parts in the axial direction from the clutch release device to the clutch release bearing.
In the above-mentioned French patent and U.S. patent the fastening means operative in traction employed generally comprise an annular coupling member which is elastically deformable in the radial direction, such as a simple ring, for example, and which is at least partially inserted radially into an annular retaining groove formed for it on either of the parts to be fastened together in traction, and a substantially transverse drive bearing surface on the other of these parts with which said coupling member cooperates in axial bearing engagement in the axial direction corresponding to the required axial coupling.
A particular advantage of an arrangement such as this is that it enables the clutch release device of the clutch to be operated to be fitted with the coupling part in advance, even before the corresponding clutch cover assembly is put together, and then, at the final assembly stage, the clutch release bearing to be engaged with the coupling part and thus with the clutch release device, by means of a simple clipping action.
Although the required coupling between the clutch release bearing and the clutch release device of the clutch to be operated is thus very easily procured, this does not apply for the converse process, meaning the process necessary to decouple the clutch release bearing and the clutch release device.
Failing other measures, it is normally necessary to demount the clutch beforehand in order to gain access from the front, that is to say from the clutch release device side, to the coupling member in order to be able to cause it to retract elastically to achieve the necessary decoupling.
To overcome this difficulty it is proposed in the aforementioned U.S. patent to use a mobile part to delimit the retaining groove; this so-called decoupling part, which is in the form of a bush, is normally spaced axially from the coupling member and it is sufficient to displace it axially towards the coupling member to expel it from the retaining groove and so bring about the necessary decoupling.
Although it has proven satisfactory, an arrangement of this kind does raise problems.
In particular, a tool is needed for maneuvering the decoupling part, which makes this maneuver relatively difficult.
In the European patent application filed Nov. 10, 1983 under the No. 83306880.2 and published under the No. 0 110 602 there is described an arrangement with which, both for decoupling and coupling, it suffices to procure appropriate axial movement of the clutch release bearing relative to the clutch release device of the clutch to be operated, the axial movement to be applied to the clutch release bearing in this way being very simple to apply blind using a control member, in practice a clutch release yoke, usually associated with it.
Using this arrangement there is associated with the coupling member an annular decoupling member which is fitted in advance to that of the parts to be fastened together in traction which comprises the drive bearing surface, at a distance from this surface, and with which said coupling member may become engaged as a result of sufficient axial movement of the clutch release bearing in the axial direction away from the bearing surface, provided that the coupling member is stressed.
The coupling member having been stressed by the decoupling member in this way, it entrains the decoupling member with it when the clutch release bearing is again subjected to an axial displacement in the axial direction towards the drive bearing surface but, because of the fact that it is stressed, it then escapes from this drive bearing surface which brings about the necessary decoupling.
However, being entrained by the coupling member, in this same movement the decoupling member itself escapes from the part to which it was initially fitted and recoupling becomes impossible unless the decoupling member is first detached from the coupling member and both these members returned to their initial position, or new members substituted for them, which entails operations that are particularly difficult to carry out.
On vehicle assembly lines it may be advantageous to be able to carry out recoupling after decoupling, however.
After coupling the clutch release bearing to the clutch release device of the clutch to be equipped, other assembly operations are carried out on such assembly lines, for example the fitting of the clutch cable controlling the assembly, and during such operations accidental action on the clutch release yoke may inadvertently decouple the clutch release bearing.
In the commonly assigned French patent application No. 85 09883 filed June 28, 1985 and published on Apr. 3, 1987, under Publication No. 2,588,051, there is proposed an arrangement permitting reversible coupling and/or decoupling to be carried out in a particularly simple and advantageous manner.
Using this arrangement there is associated with the coupling member, as previously, an annular decoupling member but this decoupling member is mounted to be movable axially in a groove from which it cannot escape.
The groove is formed in that of the parts to be fastened together in traction which comprises the drive bearing surface and the drive bearing surface forms part of one its flanks.
The decoupling member conjointly features a frustoconical bearing surface which diverges radially from the bottom of the groove in which it is disposed in the direction towards the drive bearing surface and the circumference of which axially nearest the drive bearing surface is at least level with the circumference forming the free edge of the latter.
When decoupling is required, it is sufficient, as previously, to operate on the clutch release bearing in such a way that the coupling member becomes engaged with the decoupling member.
However, this engagement of the coupling member with the decoupling member is obtained through the frustoconical bearing surface of the latter so that when the clutch release bearing is again moved axially in the axial direction towards the drive bearing surface, in order to bring about the necessary decoupling, the decoupling member which butts up against the drive bearing surface causes, through its frustoconical bearing surface and while remaining in place within the part to which it is fitted, sufficient retraction of the coupling member for the latter to escape from the decoupling member and the drive bearing surface and thus from the part comprising this drive bearing surface.
The decoupling member having remained in place, recoupling is possible.
The arrangement described in French patent application No. 85 09883 is suited only to the case where the coupling member is of one of the types described in the aforementioned French Pat. No. 2 304 826, that is to say to the case where this coupling member comprises a substantially frustoconical washer which has one of its edges engaged in the associated retaining groove and features along its other edge, substantially aligned with it, lugs through which it is adapted to cooperate in axial bearing engement with the drive bearing surface and lugs which, disposed at an angle to the aformentioned lugs, are also engaged in the retaining groove, on the side opposite the substantially frustoconical washer from which they originate.
It is not suited or not so well suited to the case where the coupling member is a simple ring, that is to say the case where the coupling member is in the form of a torus, for example in the form of a torus of circular transverse cross-section.
This is all the more so in that, with this arrangement, there is a simple bearing contact between the coupling member and the decoupling member when these two members are interlocked with each other.
Before the decoupling member butts up against the drive bearing surface, which is necessary for it to then bring about the required deformation of the coupling member, once it has been stopped in this way, it must itself be entrained by the coupling member in the direction towards the drive bearing surface.
If, as in this instance, the decoupling member features an edge through which it is interlocked with the decoupling member, the entrainment that is required beforehand can be securely obtained.
This is not necessarily so in the case of a simple ring, because of the rounded contour of the surface through which it then bears on the decoupling member.
Likewise, in French patent application No. 85 09883 there is no specific provision for the decoupling member to be axially pushed back away from the drive bearing surface when coupling takes place so as not to impede the interlocking of the coupling member with this drive bearing surface.
There may result some degree of uncertainty as to the functioning of the parts in question when coupling takes place, and in particular a certain delay in the actual effecting of such coupling, which may entail maneuvering the clutch release bearing a number of times unless, as in this instance, the coupling member is of a specific type adapted to bring about the necessary entrainment of the decoupling member in all circumstances.
Although this French patent application No 85 09883 provides for the coupling member to be carried by the drive part of the clutch release bearing or by the coupling part, the decoupling member being carried either by the coupling part or by the drive part, it has since become clear that the arrangement whereby it is the drive part of the clutch release bearing that carries the decoupling member is particularly advantageous.
For example, other things being equal it is possible to make the decoupling member longer in the axial direction because the axial space available on the drive part of the clutch release bearing is usually greater than that available on the coupling part, the latter itself having a relatively restricted axial length.
Given its greater axial length, the conditions under which the decoupling member slides on the part which carries it are improved, which minimizes the risk of it jamming on the latter.
The increased axial length of the decoupling member is not achieved at the cost of any corresponding increase in the overall axial size of the drive part and thus of an increase in the overall axial size of the assembly, the drive part itself already having sufficient axial length, given the insertion travel that it must undergo relative to the coupling part when coupling takes place, all the more so in that, as a safety measure, this travel is usually increased by an overtravel and an overtravel of this kind is also necessary when decoupling takes place.
To give the decoupling member the necessary axial length use may be made of the space usually left in the radial direction between the drive part of the clutch release bearing and the coupling means, for example a cover, axially coupling the drive member of which the drive part forms part to the maneuvering member adapted to control the assembly within the clutch release bearing.
Another advantage of the arrangement whereby the decoupling member is carried by the clutch release bearing is that the radial space which has to be provided on the corresponding drive part to permit intervention by the coupling member and which is in practice formed by the groove provided on this drive part for the decoupling member is significantly less than that which has to be provided when it has to carry the coupling member since in this case this member also has to be able to retract virtually entirely.
In the former case this space is in the order of half the radial thickness of the coupling member and in the latter case it is in the order of virtually the entire thickness.
Other things being equal, the drive part of the clutch release bearing can therefore be of smaller diameter and as it is in practice formed by one of the races of a ball bearing this results in a non-negligible saving in that the cost of a ball bearing is usually proportional to its average diameter.
Finally, using the arrangement whereby the decoupling member is carried by the drive part of the clutch release bearing the decoupling member may be fitted to the drive part either by virtue of simple elasticity or by means of a radial slit provided in it for this purpose, given that fitting it entails a temporary increase in the diameter of the decoupling member, rather than a decrease.
The arrangements may then, with advantage, be such that, with the decoupling member in place on the drive part of the clutch release bearing, there is provided between the decoupling member and the clutch release bearing an annular clearance favorable to good sliding conditions and thus to good functioning of the assembly, without there being any risk of this clearance being reduced or eliminated as a result of the radial retraction to which the decoupling member is subjected by the coupling member when it is interlocked with the latter.
For example, if the decoupling member is split radially by a slit it is sufficient for the two lips of the slit to be in contact with each other when it is in place on the drive part of the clutch release bearing.
A general object of the present invention is a clutch release bearing assembly advantageously employing an arrangement of this kind whereby the decoupling member is carried by the drive part of the clutch release bearing and advantageously exempt of the disadvantages briefly described above.